Field of the Invention
The present invention relates to a semiconductor device on which a plurality of semiconductor elements are mounted, and to a method for manufacturing the same.
Description of the Related Art
In recent years, as a variety of electronic components have been proposed and put into practice, higher and higher performance has been required for these devices. For example, the same goes for light emitting devices such as light emitting diodes (LEDs). In the fields of general lighting, on-vehicle lighting and the like, the required performance has been getting higher and higher, and there is a need for higher output (higher brightness) and higher reliability. Furthermore, there is also a need for low prices while satisfying these properties.
For example, a chip on board (COB) structure is known in the art, in which a plurality of light emitting elements are mounted on a mount area of a flat substrate, electrodes of the light emitting elements are electrically connected to external electrodes by bonding wires or the like, and the mount area is sealed with a translucent resin covering the light emitting elements and bonding wires.
For example, JP 2011-216868A discloses a light emitting device in which a plurality blue LED elements and a plurality of red LED elements are sealed with a phosphor-containing translucent resin. These blue LED elements and red LED elements are electrically connected to each other in series to form a plurality of series circuits, and the electrodes of the LED elements at both ends of each series circuit are electrically connected to a pair of external electrodes by bonding wires.
In the light emitting device of JP 2011-216868A, since the blue LED elements (hereinafter referred to as blue light emitting elements) and the red LED elements (hereinafter referred to as red light emitting elements) are electrically connected to each other in series, lighting control of these blue light emitting elements and red light emitting elements can be carried out by a single control system, which allows for simplification of its control system. However, for the purpose of achieving better color rendering properties, there is a need for a capability of separately controlling the brightness of the blue light emitting elements and the brightness of the red light emitting elements by separately controlling lighting of the blue light emitting elements and lighting of the red light emitting elements. However, separate control of the blue light emitting elements and the red light emitting elements requires separate control systems and additional external electrodes. Furthermore, the increasing number of the bonding wires from the light emitting elements to the external electrodes results in close spacing thereof. Such close spacing of the bonding wires may cause contact between the bonding wires of the blue light emitting elements and the red light emitting elements to cause deterioration of the insulation between them. Furthermore, if the external wirings are made of light-absorbing material, the optical output may be degraded.
In particular, if a plurality of light emitting elements or protection elements to be mounted on a substrate have a back-face electrode, it is required to provide a wiring to be connected to the back-face electrodes of the semiconductor elements on the mount area of the substrate. Therefore, the semiconductor elements placed at the center of the mount area require a complicated wiring pattern in the center area of the mount area. Furthermore, the insulation may deteriorate due to contact with bonding wires that are connected to the electrodes on the upper faces of the semiconductor elements. On the other hand, if the light emitting elements each have a plurality of bonding pads on the upper face, the increasing number of bonding wires may further increase the risk of deterioration of the insulation due to contact between the bonding wires.